For crypto the network overhead and variance in the exchange probably makes the performance of the order book implementation irrelevant, unless it's horribly slow, haha.
Some exchanges are doing colocation and are investing resources to greatly improve matching engine performance. It's become a little better than when they were all written in Ruby and hosted on a cheap cloud service.
Ah that's cool. Still I'd be surprised if there's many that are deterministic enough that a microsecond or two of response latency makes a big difference.
